The present invention relates to a multiple layer steel laminate gasket. More particularly, the invention relates to a multiple layer steel laminate gasket having a plurality of spacer layers sandwiched in an alternating manner between active layers and a central layer, wherein the spacer layers may be selectively removed or substituted with additional spacer layers to vary the compression ratio of a combustion engine.
Gaskets are often used to seal mating mechanical components. In one common application, a cylinder head gasket for an internal combustion engine is formed from a plurality of metallic gasket layers laminated together, with the gasket being positioned between the engine block and cylinder head of an internal combustion engine. The gasket layers are designed to have a predetermined composite thickness to maintain a desired combustion ratio for the engine. The basket layers are typically permanently secured together by welding or adhesive to provide a single gasket unit that is mounted between the engine block and cylinder head in one assembly step. Gaskets of this type are undesirable as there is no means for selectively removing gasket layers to cost-effectively increase or decrease the overall thickness of the gasket such that the compression ratio of the engine may be modified. Accordingly, to modify the compression ration of the engine a new casket assembly is required, or the engine components must be redesigned.
Therefore, there exists a need for a gasket assembly that may be selectively modified to selectively vary the overall thickness of the gasket to modify the compression ratio of an internal combustion engine.
The present invention is directed to a multiple layer gasket for sealing mating components in a combustion engine, wherein the overall thickness of the gasket assembly may be selectively varied to modify the compression ratio of the engine.
The gasket assembly has a central layer, at least two active layers and at least one selectively removable spacer layer. The active layers are preferably constructed of spring steel such that the active layers deform upon compression to seal cracks and voids in contacting surfaces. The central layer is arranged between the active layers and serves to define an initial standard, pre-determined thickness of the gasket assembly. The spacer layer is provided to vary the thickness of the gasket assembly.
The central, active and spacer layers are each provided with a plurality of corresponding apertures extending therethrough. The apertures of the respective gasket layers are positioned to be aligned with one another, as well as with corresponding apertures in the mating mechanical component being sealed, when the gasket assembly is fully assembled and positioned between the mating mechanical components. In a preferred embodiment, the active layers are positioned so as to be in contact with the mating mechanical components, while the spacer layers are sandwiched between an adjacent active layer and the central layer. Thus, the active layers serve to seal cracks and voids on mounting surfaces of the mating components, as well as sealing against imperfections on the surfaces of the spacer layers.
In accordance with the invention, one or more spacer layers may be selectively added or removed from the gasket assembly to selectively lower or increase the compression ratio of the engine, respectively. Alternatively, one or more spacer layers can be substituted with one or more additional spacer layers that have thicknesses that differ from the spacer layers positioned within the gasket assembly to selectively lower or increase the compression ratio of the engine. When it is desired to lower the compression ratio of the engine, spacer layers are either added or removed and substituted with additional spacer layers that have thicknesses that are greater than those being removed. Conversely, to increase the compression ratio, spacer layers are simply removed from the gasket assembly or spacer layers are removed and substituted with additional spacer layers having thicknesses that are less than the thicknesses of the spacer layers being removed. To achieve the maximum compression ratio for the engine, all of the spacer layers may be removed to provide a gasket assembly having a minimum thickness defined by the active layers.
Because the thickness of the respective gasket layers (central, active and spacer layers) are not clearly visible to the naked eye, it is preferred that at least the central layer be provided with a visual indicator, such as a color indicator, an alpha-numeric marking, a symbol, or the like. The visual indicator enables the respective gasket layers to be easily distinguished from one another. In one embodiment, the central layer has an elastomeric coating, in the form of a bead, extending along the periphery of the cylinder bore openings of the central gasket layer, with the elastomeric coating being dyed during the manufacturing process a first predetermined color. In addition to serving as a visual indicator to identify the central gasket layer, the bead also improves the sealing properties of the central layer. The active layers are preferably completely coated on both the top and bottom surfaces with an elastomeric coating that is dived with a second predetermined color. The elastomeric coating provides increased sealing effectiveness and a visual indicator to provide distinguishability between the action layers and the spacer and central layers. The space layers arc preferably provided with visual indications, such as indicia, to indicate the thickness of each spacer layer, thereby distinguishing the spacer layers from one another.
In accordance with another aspect of the invention, the active layers and spacer layers are removably secured together with retaining mechanisms to permit selective addition or removal of the spacer layers. In one embodiment, the retaining mechanisms include removable fasteners that extend through aligned retaining apertures formed in the active and spacer layers. Preferably, the retaining apertures are positioned adjacent a peripheral edge of the gasket layers such that the removable fasteners will not contact the mating components when the gasket assembly is positioned therebetween. Thus, sealing effectiveness will not be compromised.
In an alternative embodiment, the gasket layers are provided with aligned nesting depressions to removably secure and align the gasket layers. The nesting depressions are formed in bottom faces of the respective active and spacer layers such that an apex extends upwardly from top faces of the active and spacer layers. The apex of each nesting depression is receivable within a nesting depression of an adjacent gasket layer such that adjacent layers will be prevented from sliding apart and the gasket layers are maintained in alignment. The nesting depressions are preferably formed adjacent to or along the peripheral edge of the gasket layers such that the apex of the nesting depressions do not compromise sealing effectiveness of the gasket assembly when the gasket assembly is positioned between the mating components.
The use of the gasket assembly of the present invention permits quick and cost-effective modification of the compression ratio of an engine without having to provide a new gasket assembly or modify the engine components by adding or removing spacer layers or substituting the spacer layers with additional spacer layers of varying thicknesses. The visual indicators serve to insure proper assembly of the gasket assembly.